What is the ampacity of a 4/0 AWG THHN aluminum conductor connected to a 200-ampere rated circuit breaker?

The ampacity of a 4/0 AWG THHN aluminum conductor is determined by the conditions under which it is installed, particularly based on the National Electrical Code (NEC) guidelines. For a 4/0 AWG aluminum conductor, the ampacity is generally recognized as being capable of carrying up to 180 amperes under typical conditions.

When considering a circuit that is connected to a 200-amp rated circuit breaker, it’s crucial to be aware of the relationship between the circuit breaker rating and the conductor rating. The ampacity indicates the maximum current the conductor can safely carry without exceeding its temperature rating, which is essential for preventing overheating and potential fire hazards. In this case, while the circuit breaker itself is rated for 200 amps, the ampacity of the conductor being used is 180 amps.

It is also important to consider that circuit breakers are designed to protect the wiring in the system, and the conductor's limitations should dictate the maximum current that can be continuously drawn through it. Therefore, while the circuit breaker may allow for a maximum of 200 amps, the conductor can safely handle 180 amps, making it a suitable choice in scenarios where the load does not exceed this limit.

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